CHUGIAK, AK, USA
N825PK
PIPER PA-18
AFTER DEPARTING ON A ROUND-ROBIN, THE PILOT CONTACTED THE LOCAL AUTOMATED FLIGHT SERVICE STATION (AFSS) AND AIR-FILED A VFR FLIGHT PLAN. THE AFSS REQUESTED A PILOT REPORT ABOUT THE WEATHER CONDITIONS. THE PILOT REPORTED A SMOOTH RIDE. ABOUT ELEVEN MILES NORTH OF THE LAST RADIO CONTACT POINT, THE AIRPLANE COLLIDED WITH MOUNTAINOUS TERRAIN IN A NOSE DOWN ATTITUDE. THE PROPELLER RECEIVED MINOR DAMAGE. THE ENGINE RECEIVED EXTENSIVE FIRE DAMAGE. NO ENGINE MALFUNCTION WAS NOTED DURING A POSTACCIDENT ENGINE EXAMINATION. AN AIRMET WAS IN EFFECT WHICH STATED 'COOK INLET AND SUSITNA VALLEY...OCCASIONAL MODERATE TURBULENCE BELOW 9,000 FEET WITH ISOLATED SEVERE WITHIN 5,000 FEET ABOVE THE GROUND, ESPECIALLY THROUGH CHANNELED TERRAIN. CONTINUING BEYOND 1200.' SEARCH AIRCRAFT ALSO ENCOUNTERED MODERATE TO SEVERE TURBULENCE.
History of Flight On May 8, 1995, at an estimated time of 0905 hours Alaska daylight time, a Piper PA-18, N825PK, crashed in the Chugach Mountains, about 13 miles east of Chugiak, Alaska. The airplane was being operated as a visual flight rules (VFR) local area personal flight when the accident occurred. The airplane, registered to and operated by the pilot, was destroyed by impact and postimpact fire. The certificated commercial pilot and a passenger, received fatal injuries. Visual meteorological conditions prevailed. A VFR flight plan was filed. The flight originated at Merrill Field, Anchorage, Alaska, about 0848. After departure, the pilot contacted the Federal Aviation Administration (FAA) Kenai Automated Flight Service Station (AFSS) via radio and filed a flight plan at 0854. The pilot reported that he departed Merrill Field about 5 minutes before contacting the AFSS and was over the Alpenglow ski area (about 9 miles northeast of the departure airport). A review of voice communications between the Kenai AFSS and the pilot indicated that he requested a round robin flight plan from Merrill Field. The pilot expressed wording that indicated an intended route of flight of: Alpenglow to Sutton, Chickaloon Pass, then over the Talkeetna Mountains toward Talkeetna, back down to Point Mackenzie, and into Merrill Field. The AFSS specialist entered the flight plan route in the computer as: Merrill Field to Alpenglow, Knik Glacier, Tahneta Pass Lodge, Talkeetna, Point Mackenzie, and return to Merrill Field. The specialist also requested a pilot report (PIREP) about the weather conditions in the area. The pilot stated:..."presently at 3,500, wind is nil, beautiful flying up here, and I can see ah base of Mc Kinley, Susitna, ah nothing but good things to say". When the specialist inquired about the ride, the pilot reported that it was very smooth. No further communications were received from the pilot. The flight did not return and the Federal Aviation Administration (FAA), issued an alert notice (ALNOT) for the missing airplane at 1234. Search personnel began numerous aerial searches for the aircraft. An active search for the airplane was suspended on May 18, 1995. The wreckage was located on June 12, 1995, by a passing airplane, about 11 miles north of the pilot's last reported position. The accident occurred during the hours of daylight at lattitude 61 degrees, 21.784 minutes north, and longitude 149 degrees, 16.788 minutes west at an elevation of 4,400 feet mean sea level. Crew Information The pilot held a commercial pilot certificate with ratings for airplane single engine land and single engine sea. The most recent second-class medical certificate was issued to the pilot on April 18, 1995, and contained the limitation that the pilot must wear correcting lenses for distant vision and must possess glass for near vision. No personal flight records were located for the pilot and the aeronautical experience listed on page 3 of this report was obtained from a review of FAA airman records on file in the Airman and Medical Records Center located in Oklahoma City. On the pilot's application for an airman's medical certificate on April 18, 1995, the pilot reported that his total aeronautical experience consisted of about 3,000 hours, of which 40 hours were accrued in the preceding 6 months. Aircraft Information The airplane's recording hour meter was destroyed by impact and post-impact fire. Examination of the maintenance records revealed that the most recent annual inspection was accomplished on April 21, 1995. At that time the airplane hour meter was 2,363.2 hours. The last maintenance entry in the airframe logbook was on May 4, 1995. The hour meter was 2,365 hours. The maintenance entry included a notation that the propeller was removed for a pitch change and reinstalled. At the time of the last annual inspection on May 4, 1995, the engine had accrued a total time in service of 2,720.1 hours of operation and 771.5 hours since a major overhaul on October 2, 1986. The maintenance records for the annual inspection on April 21, 1995, included a notation that the carburetor venturi was replaced to comply with an airworthiness directive (AD) and the left magneto impulse coupling was replaced to comply with an AD. The last maintenance entry in the engine logbook on May 4, 1994, included a notation that a new spring was installed in the left magneto and then tested, and a new left magneto harness was installed. Meteorological Information The closest official weather observation station is Merrill Field, Anchorage, Alaska, which is located about 20 nautical miles southwest of the accident site. At 0852, a surface observation was reporting in part: Sky condition and ceiling, 5,500 feet scattered, measured ceiling 7,000 feet broken, 20,000 feet overcast; visibility, 50 miles; temperature, 48 degrees F; dew point, 39 degrees F; wind, calm; altimeter, 29.79 inHg; rain showers of unknown intensity southwest, northwest and north, thin spots in the overcast. The Anchorage International Airport 0855 surface observation was reporting in part: Sky condition and ceiling, 5,000 feet scattered, measured ceiling 7,000 feet broken, 10,000 feet overcast; visibility, 60 miles; temperature 45 degrees F; dew point, 38 degrees F; wind, 290 degrees at 8 knots; altimeter, 29.78 inHg; higher clouds visible, showers east and south. AIRMET "Tango" was issued by the National Weather Service (NWS) at 0645 and was valid until 1200. It stated in part: "Cook Inlet and Susitna Valley...occasional moderate turbulence below 9,000 feet with isolated severe within 5,000 feet above the ground, especially through channeled terrain. Continuing beyond 1200." Members of the Birchwood Squadron of the Civil Air Patrol (CAP) began an airborne search for the accident airplane on May 8, 1995. They reported encountering areas of moderate and occasional periods of severe turbulence in the area of the search. The weather conditions in the area were VFR. Communications A review of FAA communication records with the pilot of the accident airplane revealed that the pilot obtained a preflight weather briefing on May 6, 1995, at 0849. The pilot specified a departure point of Merrill Field, and a destination of Port Alsworth, Alaska. Review of FAA computer data revealed that the flight plan the pilot air-filed on May 8, 1995, was acknowledged by the computer at 0901. The departure time was entered as 0702. A correction to the departure time was entered in the computer at 0902 to reflect a departure time as the same as the air-file time of 0854. At 1143, the flight plan was incorrectly cancelled by AFSS personnel and then reentered at 1150. An ALNOT was entered in the computer system at 1234; however, it contained the originally incorrect departure time of 0702. A review of the air-ground radio communications tapes maintained by the FAA at the Kenai AFSS facility was utilized to obtain the pilot's recorded transmissions. A transcript of the communications is included in this report. Wreckage and Impact Information National Transportation Safety Board investigators examined the airplane wreckage at the accident site on June 13, 1995. The wreckage was located on about 30 degree upsloping tundra covered mountainous terrain at 4,400 feet mean sea level (MSL). At the time of the accident, the location was covered by snow; however, all snow had melted by the time the wreckage was discovered. At the point of rest, the fuselage was observed on a magnetic heading of 028 degrees. (All heading/bearings noted in this report are oriented toward magnetic north.) All of the airplane's major components were found at the main wreckage area. Both wings exhibited extensive spanwise leading edge aft crushing. The metal leading edge of each wing was folded flat against the vertical, forward web of each wing spar. The right wing was separated from the spar carry-through and folded aft about parallel to the fuselage. A wing inspection plate and numerous paint chips along with small melted portions of the wing covering were located on the ground outboard of the right side of the fuselage. These were oriented perpendicular to the forward wing attach point. The left wing also separated from the carry-through and was folded aft about 45 degrees. Paint chips, small melted portions of the wing covering, and the broken red position light lens were also located on the ground outboard of the left side of the fuselage. These were also oriented perpendicular to the forward wing attach point. Both lift struts remained attached to their respective wings and lower attach points and both were folded in an aft direction. Both main landing gear were bent in an aft direction. The metal wing mounted fuel tanks remained attached to their respective internal attach points. The left wing tank exhibited outward bulging of the tank walls with separation and fire damage evident on the inboard side of the tank. The left fuel tank cap remained in place on the upper side of the tank. The right wing fuel tank exhibited similar outward bulging of the tank walls with separation and fire damage to the inboard side of the tank. The right fuel tank cap was located on the ground, about 6 feet to the left of the engine. A postcrash fire incinerated the cabin/cockpit area. All of the airplane's fabric covering was melted from the airframe with the exception of about 3 feet of the outboard ends of each wing, the rudder, and portions of the underside of each elevator. Several small fragments of plexiglass were located forward of the nose of the airplane. Additional fragments were located to the left of the engine. The flight control surfaces remained connected to their respective attach points. The horizontal stabilizer trim actuator was found extended about 10 threads above its lateral mounting bracket. According to the airplane manufacturer, the extended stabilizer actuator corresponded to a 1.4 degree nose down (stabilizer leading edge up) setting, and was 36 percent of available trim. Due to the impact and postimpact fire damage, Safety Board investigators were unable to operate the flight controls by their respective control mechanisms; they were, however, able to establish continuity of the flight control cables to the cockpit. The propeller assembly remained connected to the engine crankshaft. The spinner was crushed flat against the hub. One propeller blade was relatively straight. Both blades exhibited chordwise scratching on the cambered side of the blade, aft from the leading edge about 2 inches. The scratching was evident from the hub, outboard for about 12 inches. The second propeller blade was bent aft about a 45 degree angle, about 8 inches outboard from the hub. It also exhibited minor trailing edge gouging. The engine sustained impact damage to the underside/front portion of the engine. The engine cowling was crushed upward against the bottom of the engine. A portion of the tundra was scraped in a forward direction under the engine cowling. The left aft end of the exhaust tube was separated from the muffler and exhibited about a 180 degree bend with smooth folds without cracking. The right front exhaust tube was crushed aft and formed around the lower spark plug. The crankshaft could be rotated slightly by hand at the propeller; however, due to the angle of the terrain, 360 degree rotation was not achieved. The magnetos sustained fire damage and could not be functionally tested. Examination of the top cylinder sparks plugs revealed a dry and grey appearance. Medical and Pathological Information A postmortem examination of the pilot was conducted under the authority of the Alaska State Medical Examiner, 5700 E. Tudor, Anchorage, Alaska, on June 14, 1995. The medical examiner indicated that no specimen suitable for toxicologic analysis was recovered and the examiner elected not to perform a microscopic examination. Survival Aspects An extensive search was conducted for the airplane by units of the military and members of the Civil Air Patrol (CAP). No emergency locator transmitter (ELT) signal was received from the airplane. Examination of the ELT at the wreckage site revealed impact and fire damage to the case. Tests and Research After the airplane was recovered, Safety Board investigators conducted an engine examination on June 28, 1995. The parties noted in this report participated in the examination. Gear and valve train continuity was established and thumb compression in each cylinder was noted, when the crankshaft was rotated by hand. The engine cylinders and pistons did not exhibit any damage. The engine accessory gear case was extensively damaged by fire. The magnetos were destroyed by fire. The exhaust tubes on the left side of the engine exhibited sharp breaks near the attach point of the cylinders. The previously observed exhaust tubing formed around the number 1 cylinder spark plug was removed and it exhibited sharp, broken edges adjacent to the plug. The carburetor sustained impact and external fire damage. The bowl separated from the upper half of the carburetor and the float assembly was not located. The fuel nozzle was broken and the venturi was broken in half. The carburetor inlet fuel screen was free of contaminants. The engine fuel strainer separated from its attach points and the screen was free of contaminants. The oil suction and oil pressure screens exhibited some melting of the solder joints but were free of contaminants. The crankshaft flange runout was measured at .020 inches. Additional Information Wreckage Release The Safety Board released the wreckage, located at Big Lake, Alaska, to the owner's representatives on June 28, 1995. No parts or components were retained by the Safety Board.
THE PILOT'S FAILURE TO MAINTAIN ADEQUATE AIRSPEED RESULTING IN AN INADVERTENT STALL. THE PILOT'S FAILURE TO OBTAIN A WEATHER BRIEFING AND AN ENCOUNTER WITH TURBULENCE WERE FACTORS IN THE ACCIDENT.
Source: NTSB Aviation Accident Database
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